1. Field of the Invention
The present invention relates to an image processing device and an image processing method.
2. Description of the Related Art
There has been known a scanner device for reading an original and converting it into digital data. The scanner device is also provided in, for example, a copying device, a printer device, a facsimile device, a multifunction device provided with any two of the above, or the like. In recent years, the scanner device has a mechanism for reading front and back sides of a double-sided original simultaneously in paper feeding at once (i.e., one-pass double-sided simultaneous reading mechanism) through an original reading unit. By using the scanner device having this mechanism, it is possible to read two sides in a period of time for reading one side, whereby productivity can be improved.
The scanner device having this function is capable of reducing a reading time, but it is necessary to parallelize image processing of image data of two sides, whereby a total cost is increased. To solve this problem, there has been proposed a scanner device in which an inexpensive local memory is arranged. The scanner device temporarily accumulates the read images of two sides in the local memory, performs the image processing one side by one side in order, and transfers it to an output device. In this way, the scanner device having this mechanism is capable of improving the productivity of reading the double-sided original while decreasing the total cost.
Note, however, that in the one-pass double-sided simultaneous reading mechanism, a sensor of the original reading unit is physically different between that for a front side and that for a back side, whereby color tone and the like of the read image data are different between the front side and the back side. Accordingly, it is necessary for the scanner device having this mechanism to perform the image processing one side by one side in order by alternately switching a parameter used for image quality adjustment between image processing of the front side and image processing of the back side.
Prior to execution of the image processing, the parameter used for image quality adjustment is transferred from a main memory to a target register. Therefore, the conventional scanner device is provided with a specialized parameter direct memory access controller (DMAC) for rewriting the parameter. Thus, in the conventional scanner device, overheads of parameter rewriting performed between the image processing of the front side and image processing of the back side is decreased while a processing load of a central processing unit (CPU) is also reduced.
A conventional parameter DMAC starts transfer of a parameter as soon as it receives a start instruction from a CPU. Therefore, it is necessary for the CPU to manage start timing of the parameter DMAC by following a software program and the like. However, in order for the CPU to detect the start timing, it is necessary to execute, for example, receiving an interruption signal or reading a register, which required processing time.
Furthermore, in a case where one parameter DMAC is used commonly by a scanner and a plotter, or in a case where one parameter DMAC is used commonly by a plurality of pieces of color plane data, it is necessary for the CPU to check whether or not the parameter DMAC is used for a different purpose and to determine priority of each processing, thereby giving the start instruction to the parameter DMAC. Moreover, there is a possibility of access competition since both of the CPU and the parameter DMAC access the register. Accordingly, the CPU needs to manage an operation condition of the parameter DMAC, whereby control thereof has been complicated.
Therefore, there is a need for an image processing device and method capable of reducing load on a processor without making the processor such as the CPU to manage timing of transfer of a parameter used in image processing.